It is controversial whether AF PGs increase before parturition in women and non-human primates. Previous studies in rhesus monkeys that were chronically catheterized with maternal and fetal vascular and AF catheters, fetal ECG and myometrial EMG electrodes indicate a pre-partum rise in AF PGs (SGI, 1994 Abst# P208). To determine if catheterization leads to increased AF PG levels due to inflammation of fetal membranes or decidua, we modified the AF collection procedure. Five animals received only 2 AF catheters (PORTAL) modified to remain subcutaneous thus reducing surgical intervention, eliminating restraint devices (jacket and tether) and the continuous exposure of catheters. AF was collected from 3 additional animals by amniocentesis (AMNIO). AF was collected weekly until Day 150 of pregnancy, then every 1 to 3 days until delivery. Impending delivery was determined by cervical status. AF cultures for facultative and anaerobic organisms were performed. PG concentrations were determined by specific EIA (Cayman Chemical). Animals instrumented with only portal catheters showed average AF PGE2 concentrations of 532.1 + 80.8 pg/ml prior to day -10 and increased to peak levels of 2951 + 531 pg/ml prior to delivery. AF PGF2` levels from PORTAL animals averaged 92.7 + 11.3 pg/ml and increased to 591.5 + 298.2 pg/ml before delivery. Similar levels were obtained in AMNIO animals. Results grouped into weekly data are shown below. Amniotic Fluid Prostaglandin Concentrations (pg/ml) Weeks CHRONIC PORTAL AMNIO Prepartum PGE2 PGF2` PGE2 PGF2` PGE2 PGF2` 1 2765 q 782 708 q 89 1995 q 291 398 q 78 1749 q 634 352 q33 2 1032 q 348 399 q 43 955 q 164 159 q 21 1309 q 484 174 q42 3 427 q 196 285 q 38 545 q 97 92 q 16 389 q 134 69 q24 The increase in AF PGs seen prior to parturition in rhesus monkeys is not related to infection or chronic catheterization.